Resistance-sheet for electric heaters or rheostats.



No. 768,764. PATENTED AUG. 30, 1904,

G. I. LEONARD.

RESISTANCE SHEET FOR ELECTRIC HEATERS OR RHEOSTA'TS.

. APPLICATION FILED SEPT. 9, 1908. NO MODEL.

UNITED STATES Patented August 30, 1904.

PATENT OEEIcE.

GEORGE I. LEONARD, OF PASADENA, CALIFORNIA.

SPECIFICATION forming part of Letters Patent No. 768,764, dated August30, 1904.

Application filed September 9, 1903. Serial No. 172,452. (No model.)

T 0 all 1072,0777, it worry concern:

Be it known that I, GEORGE I. LEONARD, a citizen of the United States,residing at Pasadena, in the county of Los Angeles and State ofCalifornia, have invented anew and useful Resistance-Sheet for ElectricHeaters or Rheostats, of which the following is a specification.

Heretofore rheostats or heaters have been constructed by stretchingresistance-wire incoils or by weaving it back and forth between pins orsupports. In such a construction when a wire breaks, the wire beingunder tension, it snaps and becomes entangled with other wires and formsshort circuits which cause a great deal of trouble and expense.

The main object ofthe present invention is to obviate this difficultyand to provide a resistance-sheet so constructed that the sheet itselfmay be held under atension; but the current-carrying element issupported by the sheet in such a manner that if the currentcarryingelement burns out it does so quietly without interfering with any of theother sheets or parts of the heater.

Another object is to so combine the resistance-wire or othercurrent-carrying element with the sheet that the sheet is uniformlyheated throughout its entire area on both faces, so that thedistribution of heat from the sheet is practically uniform at allpoints.

The accompanying drawings illustrate the invention, and referring to thesame, Figure I is a perspective view of a rheostat or electric heaterconstructed with my improved resistance. Fig. II is a sectional viewthrough the supporting-sheet, showing one manner in which theresistance-wire may be stitched therethrough. Fig. III is a view similarto Fig. II, showing another mode of stitching. Fig.1V is a plan viewshowing a disk form of sheet adapted for use in another form of heateror rheostat.

Briefly, the invention comprises a supporting medium, preferably insheet form, and of an electrical non-conductor which is composed of somenon-fusible material-such, for instance, as asbestos or mica-withresistancewire stitched into or through the supporting medium.

In the drawings, 1 designates the supportpiece of cloth.

stitch, or it may be the ordinary plain stitch,

as shown in Fig. II. coarse or fine.

The stitches may be In Fig. I a series of rectangular sheets rf'e shownheld in avertical position by supports 3, mounted on a base at, andopposite ends of the wire, which is stitched through a sheet, areconnected to metallic strips 5 on the edges of the sheets. The stripsconduct the electric current from the supports 3 and also serve tostiffen the edges of the sheets. The supports 3 are preferably of aspring metal, so as to place the sheets under a tension suificient tohold the sheets flatly.

The wire may be stitched back and forth, as shown in Fig. 1, preferablywith sufiicient space between the rows to prevent arcing, and it isobvious that the wire could be stitched up and down in vertical rows onthe sheet instead of lengthwise of the sheet, as shown. The wire ispreferably sewn into the sheet with a sewing-machine just as one wouldstitch a thread with a sewing-machine through a In this manner the wireis bent sharply at its junctions with the sheet and is stretched tight.The perforations through which the wire passes are in rows, and theperforations in a row are close together, and the wire is led from oneperforation in a row directly to the adjacent perforation in the samerow, and so on throughout the row. The wire then leaves that row andstarts on another row, being passed through the "perforations in eachrow serially. In other words, the perforations of a row serially receivethe wire, thus forming a row of continuous stitches.

By reason of the wire being stitched so as to spread over the surface ofthe sheet the heat is prevented from concentrating, but is spread outand radiated in the most efiective manner possible, which isadvantageous whether the resistance is used for a rheostat or for aheater. The wire is supported permanently in position by the sheet, andif a wire breaks or burns out the trouble is merely local and does notaffect the rest of the heater, and the wires cannot possibly becometangled. Moreover, the wire itself is not under a tension, as it is thesupporting-sheet which is stretched flatly, and if the wire burns out itdoes so quietly and without interfering with other parts.

The disk form of sheet shown in Fig. IV is designed especially for usebetween metallic substances to form disk heaters or other similar forms.

It is obvious that repairs may readily be made by substituting a newsheet in the event that the wires of the sheet burn through.

W hat I claim, and desire to secure by Letters Patent of the UnitedStates, is

1. Supporting means and a resistance material sewn with a row ofcontinuous stitches into the supporting means.

2. A sheet of non-conducting material and resistance sewn with a row ofcontinuous stitches into the sheet.

3. A sheet of non-fusible material and resistance sewn with a row ofcontinuous stitches into the sheet.

4:. A sheet of non-conducting, non-fusible material and resistance sewnwith a row of continuous stitches into the sheet.

5. A sheet of asbestos and resistance-wire sewn with a row of continuousstitches through the sheet.

6. A sheet, and resistance-wire sewn with a plurality of rows each rowbeing formed of continuous stitches.

7. An exposed sheet, and resistance material sewn through the sheet.

8; An exposed sheet, and a bare resistancewire sewn through the sheet.

In testimony whereof I have hereunto set my hand, in the presence of twosubscribing witnesses, this 1st day of September, 1903, at Los Angeles,in the county of Los Angeles and State of California.

GEO. I. LEONARD.

Vitnesses:

GEORGE T. HAOKLEY, JULIA TOWNSEND.

